Why is this even an issue? Sure, there are equine images that are overly twee for my taste. Then, there is the horse screaming in the center of Guernica. Art lies in the treatment of the subject, not the subject itself.
I found the badge here while trawling deviantART. The creator invited passersby to share, “Help stop the discrimination of equine artists by putting this in your journal.”
Virtual Brush Box 
Mystified, too….
Although many equine artists “sell out” when doing commission work and produce those twee images you refer to, they are still able to follow their own style when doing exhibitions etc
of course it is!
Meh. People get their knickers in a wad about all sorts of non-issues. But, you know, glad you’re on the bandwagon. š